Modelling Percolation

The phenomenon of 'percolation' the passage of fluid or gas through solids of varying permeability, also has relevance to spread of diseases or polymerisation. The article stimulated me to animate the process as I found the article' static diagrams rather weak for helping understanding!

I create a rectangular grid representing nodes linked to their four neighbours ( or an edge). I then block these with a chosen probability- eg 0.5 means on average half the links are blocked. 100% is no-connections. 0% means 'no links obstructed'.

I then find in turn all entry links which are open, and follow each to the end of all connections that are open- or until it reaches the far-left side.

In the animation below, you can see how far the blue 'water' gets for ten different probabilities.

LB code for one version

    nomainwin

    global offset
    offset       = 50
    Rand         =  0.6    '   probability crack is open

    WindowWidth  =640
    WindowHeight =630

    open "Percolation" for graphics_nsb as #wg

     hw      =hwnd( #wg)
     calldll #user32, "GetDC", hw as ulong, hdc as ulong

     #wg "trapclose quit"

for Rand =0.00 to 1.00 step 0.1
    #wg "cls ; down"
    #wg "backcolor 255 0 0 ; fill 192 192 192"
    call delay 100
    #wg "place "; offset; " "; 0
    #wg "boxfilled "; offset +610; " "; 610

    call makeGrid

    call changeLink Rand

    #wg "size 10 ; color black ; down ; set 620 300"
    'targetcolor   =192 +192 *2^8 +192 *2^16
    targetcolor   =int( 255 +0 *2^8 +0 *2^16)   '   to fill out to or within. Here RED.
    x   =620:     y   =320  '   fill with blue water from near the black spot.

    #wg "backcolor 150 150 255"

    #wg "size 3"

    call delay 1000

    calldll #gdi32, "ExtFloodFill",_
            hdc                as ulong,_
            x                  as long,_
            y                  as long,_
            targetcolor        as long,_
            _ '_FLOODFILLSURFACE  as  long, result as  long 'ie fill out 'WHILE this colour is met.
            _FLOODFILLBORDER   as  long, result as  long 'ie fill out 'til this colour is met..

    #wg "place 8 60 ; color red ; backcolor 192 192 192"
    #wg "\"; using( "#.###", Rand)
    #wg "flush ; getbmp scr 1 1 630 600"
    bmpsave "scr", "rocks_" +str$( Rand) +".bmp"

    call delay 1000
next Rand

    wait

    sub makeGrid
        #wg "color 192 192 192 ; size 3"
        for x =offset +0 -10 to 610 step 10
            #wg "line "; x; " "; 0; " "; x; " "; 600
        next x

        for y =0 -10 to 600 step 10
            #wg "line "; offset; " "; y; " "; offset +560; " "; y
        next y

        #wg "backcolor 192 192 192 ; up ; goto 612 0 ; down ; boxfilled "; 630; " "; 630
        #wg "backcolor 192 192 192 ; up ; goto   0 0 ; down ; boxfilled ";  50; " "; 630
        scan
    end sub

    sub changeLink probability
        #wg "color 255 0 0"
        #wg "size 10"
        for x =offset +5 to offset +550 step 10
            for y =0 to 600 step 10
                if probability <=rnd( 1) then #wg "set "; x +5; " "; y
            next y
        next x
        scan
    end sub


    sub delay sleeptime
        calldll #kernel32, "Sleep", sleeptime as long, ret as void
        scan
    end sub

    sub quit h$
        calldll #user32, "ReleaseDC", hw as ulong, hdc as ulong, ret as void   'release the DC
        close #h$
        end
    end sub